The present invention relates generally to power transmission chains. The invention has particular application to power transmission chains of the roller chain variety, which are used primarily in automotive engine timing applications, but also can have automotive applications in the transfer of power from a torque converter to a transmission or in a transfer case of a four-wheel drive vehicle.
One type of chain is known as "roller chain". A typical roller chain consists of alternate inner links and outer links. The inner links, which are also known as "bushing" links, consist of spaced sidebars with bushings tightly received in openings, or apertures, at each end of the sidebars. The outer links, which are also known as "pin" links or "guide" links, consist of spaced sidebars with pins tightly received in openings, or apertures, at each end of the sidebars. The bushings freely rotate about the pins to pivotally connect the outer links to the inner links in alternate arrangement. Rollers are provided on the bushings, and when the roller chain is wrapped about a sprocket, the teeth of the sprocket are received between the laterally spaced sidebars and the longitudinally spaced rollers. Examples of roller chain are found in U.S. Pat. Nos. 4,186,617 and 5,226,856, which are both incorporated herein by reference.
Roller chain drives can include both "true roller" and rollerless design. The true roller design includes the described rollers mounted about the bushings. Rollerless chain contains bushings that directly contact the sprocket. Both types of roller chain are typically specified in industry as British Standard chain and American National Standards Institute (ANSI) chain.
In conventional roller chain, outside links or pin links are press fit on the pins. The pins typically extend out beyond the edges of the outside links in the transverse direction of the chain, i.e., the direction transverse to the longitudinal movement of the chain around the sprockets.
As explained below, in one embodiment of the present invention, the pins are flush with the outside edges or sides of the outside links or pin links, or are constructed for minimal projection from the sides of the outside links. Minimization of the projection of the pins allows a narrower chain construction and permits embodiments where the outer links of two chains in side-by-side relation may be combined in a single assembly, or may be in contacting relation. Additionally, in another embodiment, the pins of two adjacent chains are in a contacting relationship, or the pins of one chain contact the sides of the outside links of the adjacent chain.
The present invention has particular application to chain assemblies in which the chains and sprockets are offset, or phased, to modify the impact noise spectrum and chordal action noise spectrum. In a phased chain system, a single chain assembly is divided into, or replaced by, two side-by-side chains that are phased or offset typically by one-half pitch. In one embodiment of the present invention, the minimal pin projection is utilized on the sides of the two chains that are in the side-by-side relationship. Running the two chains in a side-by-side and touching relationship, allows the achievement of a narrower phased chain system than in certain phased chain systems of the prior art.
A conventional roller chain drive is comprised of an endless roller chain wrapped about at least two sprockets supported by shafts. Rotation of a driving sprocket causes power transmission through the chain and consequent movement of a driven sprocket. In an engine timing drive application, the driving sprocket is mounted on the engine crankshaft and the driven sprocket mounted on the camshaft. Various types of engine timing systems and configurations, which are suitable for roller and inverted tooth chain assemblies, are also shown in U.S. application Ser. No. 08/131,473, filed Oct. 4, 1993, now U.S. Pat. No. 5,427,580 which is incorporated herein by reference.
Noise is associated with chain drives. Noise is generated by a variety of sources, but in roller chain drives it can be caused, in part, by the impact sound generated by the collision of the chain and the sprocket at the onset of meshing. The loudness of the impact sound is affected by, among other things, the impact velocity between the chain and the sprocket and the mass of chain rollers contacting the sprocket at a particular moment or time increment.
Many efforts have been made to decrease the overall noise level and pitch frequency noise distribution in automotive chain drives to minimize the objectionable effects of the pure sonic tones. Several of those efforts are discussed in the above-mentioned U.S. application Ser. No.08/131,473, filed Oct. 4, 1993. The present invention finds application along with some of the noise reduction concepts discussed in the above-mentioned application, including randomization and phasing of the chain assemblies. However, the present invention has broader applications to chain systems that include, for example, non-phased sprockets.
Phasing the chain and sprocket relationship can reduce the number of chain rollers (or mass) impacting the sprocket during a given time increment. Similarly, phasing the chain and sprocket relationship can alter or phase the chordal action or articulation of the chain and sprocket.
However, in the narrow chain assembly package requirements that are particularly found in modern engine timing systems, the use of a phased chain system can be difficult in that the single chain is often replaced by two chains that are placed in side-by-side and phased relation. The need to place two phased chains in side-by-side relationship in the same width previously occupied by a single chain requires elimination of some links or use of thinner links. Such a modification is disadvantageous in that it uses fewer links across the width of the chain, or thinner links across the chain, which generally results in a weaker chain assembly than the assembly with a greater number of links across the width of the chain.
Phased chain systems as well as side-by-side non-phased chain systems are conventionally constructed with the two chains in a spaced-apart relationship. The spacing is provided between the two chains to assure that the chains do not contact one another during operation. In high speed automotive applications, significant movement occurs in the portions of each chain that span the longitudinal space between the driving and driven sprockets of each assembly. The separation between the two chains in the transverse direction is provided to prevent any contact between the two chains during such movement. Clearances between the chain and other structures are typically recommended in order to avoid contact from longitudinal or transverse movement of the chain during operation. The separation distance between the chains also contributes to the size or overall width of the chain package.
As noted above, the present invention utilizes pins that are constructed for minimal projection from the sides of the chains. An example of a roller chain that utilizes welded side bars to avoid extension of the pins beyond the edge of the outside links is shown in U.S. Pat. No. 4,036,072 to McKeon et al. In the McKeon et al. chain, the ends of the pins are welded in abutting relationship with the inner faces of the side bars.
An example of a phased roller chain system is disclosed in U.S. Pat. No. 3,029,654 to Hill. In the Hill patent, three roller chains are placed in a side-by-side but offset or phased relationship. The three chains are shown with pins that project transversely from the links. The three chains are shown in a spaced-apart relationship in the transverse direction, which avoids contact between the chains and the pins.
Another example of a phased roller chain system is disclosed in Japanese publication no. 3-28348 (application no. 1-51359) to Kawakami. In the Kawakami system, four chains are placed in side-by-side relationship, but offset or phased by one-quarter pitch. The Kawakami reference teaches that the chains are not connected to one another, but are independent. While FIG. 3 of Kawakami appears to disclose contact between the pins on adjacent chains, this contact may be only an incidental contact in view of Kawakami's teaching of independent chains. Moreover, on account of the one-quarter pitch offset, the pins do not nest within each other and do not contact the links of the adjacent chain. The Kawakami chain construction is very similar to the system shown in Japanese publication no. 5-17251 (application no. 3-90363).
A third example of a phased roller chain system is disclosed in Japanese publication no. 2-76944 (application no. 63-227318) to Fukumoto. The Fukumoto application discloses two phased roller chains that are interconnected by protruding pins. FIG. 2 of Fukumoto illustrates the chains in a close relationship, while FIG. 4 of Fukumoto illustrates the chains further apart, but still interconnected by protruding pins. Fukumoto teaches interconnection of the two chains and does not show the chains in an unconnected or independent relationship.